Contextual modulation of hippocampal activity during picture naming.

Picture naming is a standard task used to probe language processes in healthy and impaired speakers. It recruits a broad neural network of language related areas, among which the hippocampus is rarely included. However, the hippocampus could play a role during picture naming, subtending, for example, implicit learning of the links between pictured objects and their names. To test this hypothesis, we recorded hippocampal activity during plain picture naming, without memorization requirement; we further assessed whether this activity was modulated by contextual factors such as repetition priming and semantic interference. Local field potentials recorded from intracerebral electrodes implanted in the healthy hippocampi of epileptic patients revealed a specific and reliable pattern of activity, markedly modulated by repetition priming and semantic context. These results indicate that the hippocampus is recruited during picture naming, presumably in relation to implicit learning, with contextual factors promoting differential hippocampal processes, possibly subtended by different sub-circuitries.

The contribution of frequency-specific activity to hierarchical information processing in the human auditory cortex.

The fact that feed-forward and top-down propagation of sensory information use distinct frequency bands is an appealing assumption for which evidence remains scarce. Here we obtain human depth recordings from two auditory cortical regions in both hemispheres, while subjects listen to sentences, and show that information travels in each direction using separate frequency channels. Bottom-up and top-down propagation dominates in γ- and δ-ß (<40 Hz) bands, respectively. The predominance of low frequencies for top-down information transfer is confirmed by cross-regional frequency coupling, which indicates that the power of γ-activity in A1 is modulated by the phase of δ-ß activity sampled from association auditory cortex (AAC). This cross-regional coupling effect is absent in the opposite direction. Finally, we show that information transfer does not proceed continuously but by time windows where bottom-up or top-down processing alternatively dominates. These findings suggest that the brain uses both frequency- and time-division multiplexing to optimize directional information transfer.

Differential role of visuospatial working memory in the propensity toward uncertainty in patients with obsessive-compulsive disorder and in healthy subjects.

BACKGROUND: Obsessive-compulsive disorder (OCD) is associated with visuospatial working memory deficits. Intolerance of uncertainty is thought to be a core component of OCD symptoms. Recent findings argue for a possible relationship between abilities in visuospatial memory and uncertainty. However, this relationship remains unclear in both OCD patients and healthy subjects. To address this issue, we measured performance in visuospatial working memory and the propensity to express uncertainty during decision making. We assessed their relationship and the temporal direction of this relationship in both OCD patients and healthy subjects. METHOD: Baseline abilities in visuospatial working memory were measured with the Corsi block-tapping test. A delayed matching-to-sample task was used to identify explicit situations of certainty, uncertainty and ignorance and to assess continuous performance in visuospatial working memory. Behavioural variables were recorded over 360 consecutive trials in both groups. RESULTS: Baseline scores of visuospatial working memory did not predict the number of uncertain situations in OCD patients whereas they did in healthy subjects. Uncertain trials led to reduced abilities in visuospatial working memory to 65% of usual performance in OCD patients whereas they remained stable in healthy subjects. CONCLUSIONS: The present findings show an opposite temporal direction in the relationship between abilities in working memory and uncertainty in OCD patients and healthy subjects. Poor working memory performance contributes to the propensity to feel uncertainty in healthy subjects whereas uncertainty contributes to decreased continuous performance in working memory in OCD patients.

Navigated rTMS for the treatment of tinnitus: a pilot study with assessment by fMRI and AEPs.

OBJECTIVE: Repeated transcranial magnetic stimulation (rTMS) of auditory cortex has been proposed to treat refractory chronic tinnitus, but the involved mechanisms of action remain largely unknown. The purpose of this pilot study was to evaluate the impact of rTMS on auditory cortex activity in a series of tinnitus patients, using for the first time both functional magnetic resonance imaging (fMRI) of the brain and auditory evoked potentials (AEPs). METHOD: In six patients with chronic, lateralized refractory tinnitus, we performed five sessions of neuronavigated rTMS delivered at 1Hz over the secondary auditory cortex (defined on morphological MRI), contralateral to tinnitus side. The effects of rTMS were assessed on clinical scales, fMRI, and AEPs (N1 and P2 components). RESULTS: The clinical impact of rTMS on tinnitus was good for three patients (25-50% improvement of tinnitus severity compared to baseline), moderate for two patients (15% improvement), and null for one patient who had the most severe tinnitus at baseline. The changes induced by rTMS on fMRI data varied with the baseline level of auditory cortex activation before rTMS. This baseline level of activation was itself related to the severity of tinnitus. Thus, cortical stimulation increased auditory cortex activation in patients who had less severe tinnitus and low level of activation before rTMS, whereas it decreased auditory cortex activation in patients who had more severe tinnitus and higher level of activation before rTMS. Regarding AEPs, rTMS decreased N1 amplitude in all patients, except in the patient who had the most severe tinnitus at baseline and showed no improvement after rTMS. Conversely, P2 amplitude decreased after rTMS only in patients with severe tinnitus, at least for auditory stimulation contralateral to tinnitus, but increased in patients with less severe tinnitus. CONCLUSIONS: The changes produced by rTMS in auditory cortex activity, as assessed by fMRI and AEPs, appeared to depend on a process of disease-related homeostatic cortical plasticity, regardless of the therapeutic impact of rTMS on tinnitus.

Performance in recognition memory is correlated with entorhinal/perirhinal interictal metabolism in temporal lobe epilepsy.

In addition to the hippocampus, the entorhinal/perirhinal cortices are often involved in temporal lobe epilepsy (TLE). It has been proposed that these anterior parahippocampal structures play a key role in recognition memory. We studied the voxel-based PET correlation between number of correctly recognized targets in a new recognition memory paradigm and interictal cerebral metabolic rate for glucose, in 15 patients with TLE with hippocampal sclerosis. In comparison to healthy subjects, patients had decreased recognition of targets (P<0.001) and ipsilateral hypometabolism (relative to side of hippocampal sclerosis) of the hippocampus, entorhinal/perirhinal cortices, medial temporal pole, and middle temporal gyrus (P<0.05, corrected by false discovery rate method). Performance correlated with interictal metabolism of ipsilateral entorhinal/perirhinal cortices (P<0.005, Spearman's rank test), but this relationship was not significant in the hippocampus itself (P>0.18, Spearman's rank test). These findings highlight the preferential involvement of entorhinal/perirhinal cortices in recognition memory in patients with TLE, and suggest that recognition memory paradigms may be useful in assessing anterior parahippocampal functional status in TLE.

Exercise testing and exercise stress echocardiography in asymptomatic aortic valve stenosis.

Management of asymptomatic patients with severe aortic valve stenosis (AVS) remains a source of debate. Exercise testing is no longer contraindicated and needs now to be considered when evaluating asymptomatic patients with AVS. Several studies have clearly demonstrated that exercise-elicited symptoms during conventional upright exercise portends clinical events. Semi-supine exercise with continuous Doppler echocardiography monitoring elicits cardiovascular abnormalities that are not detected at rest. Abnormal left ventricular response to exercise and/or major increase in mean transvalvular gradient add to the prognostic value of elicited symptoms in asymptomatic patients with severe AVS. However, preliminary experience needs to be confirmed to warrant routine use of exercise Doppler echocardiography in the evaluation of patients with asymptomatic AVS.

Asymmetry of voice onset time-processing in adult developmental dyslexics.

OBJECTIVE: The human auditory cortex codes speech temporally according to sequential acoustico-phonetic cues like the voice onset time (VOT). This coding is predominantly left-lateralized in normal readers. We examined VOT-processing asymmetries in adults with a history of developmental dyslexia (DD-history+). METHODS: Auditory-evoked potentials (AEPs) to voiced (/ba/) and voiceless (/pa/) speech stimuli were recorded from 10 DD-history+ adults and 8 controls. Source modelling of the "release component" (RC: approximately 240 ms; time-locked to voiced consonantal release and considered reflective of VOT-processing) was conducted to explore VOT asymmetries. RESULTS: Controls demonstrated L>R RC source probe amplitude asymmetry in the auditory cortex. DD-history+ subjects with little persistent reading deficit (n=5) demonstrated normal temporal coding but rightward asymmetry. DD-history+ subjects with severe persistent deficits (n=5) exhibited numerous supplemental AEP components (notably left hemispheric) and inconsistent asymmetry (leftward or alternating). CONCLUSIONS: These preliminary findings suggest that DD-history+ adults process auditory speech cues differently than adults without previous DD. The nature of this processing may relate to the severity of persistent reading deficits. SIGNIFICANCE: Previous dyslexics with little persistent deficit can exhibit atypical functional asymmetry with normal auditory temporal coding. Source modelling represents an effective, non-invasive means of exploring processing asymmetries in clinical populations.

[Kimura's disease associated with extracapillary glomerulonephritis]. / Maladie de Kimura associée à une glomérulonéphrite extra-capillaire nécrosante.

BACKGROUND: Kimura's disease is a rare and benign chronic inflammatory soft-tissue disorder of unknown origin. Most cases involve young Asian males. The typical presentation consists of painless papules or nodules with a predilection for the head and neck region, associated with lymphadenopathy, parotid gland involvement, peripheral blood eosinophilia and raised immunoglobulin E. PATIENTS AND METHODS: A 49-year-old Mauritian man was hospitalized for nephrotic syndrome. Examination revealed a painless 3 cm nodule in the left pre-auricular region and multiple enlarged left cervical lymph nodes. Histopathologic examination of a nodule confirmed the diagnosis of Kimura's disease, which was associated with necrotic extracapillary glomerulonephritis. Corticosteroids were initiated, resulting in rapid improvement of renal function and partial regression of the patient's cutaneous nodules and lymph node disorder. DISCUSSION: Renal manifestations are the only visceral localization of Kimura's disease, and proteinuria is seen in 12% of cases, of which 50% are accompanied by nephrotic syndrome. Many different histologic types of renal involvement may be observed with potentially severe lesions. To our knowledge, this is the first case of Kimura's disease associated with extracapillary glomerulonephritis.

[Mild aortic stenosis and coronary bypass surgery]. / Sténose aortique modérée et pontages aortocoronaires.

The presence of mild to moderate aortic stenosis in a patients scheduled for coronary bypass surgery poses difficult problems with respect to the optimal therapeutic strategy. The first step is obviously to obtain a precise quantification of the degree of stenosis. Whenever possible, confrontation with previous echo examinations will provide an idea of the speed with which aortic stenosis progresses. The cardiologist, together with the cardiac surgeon, will have to carefully balance the operative risk and the risk of a second intervention. The patient's age will be central in the discussion, as it is a major determinant of life expectancy after the initial intervention.

Effects of GSM signals on auditory evoked responses.

The article presents a study of the influence of radio frequency (RF) fields emitted by mobile phones on human cerebral activity. Our work was based on the study of Auditory Evoked Potentials (AEPs) recorded on the scalp of healthy humans and epileptic patients. The protocol allowed us to compare AEPs recorded with or without exposure to RFs. To get a reference, a control session was also introduced. In this study, the correlation coefficients computed between AEPs, as well as the correlation coefficients between spectra of AEPs were investigated to detect a possible difference due to RFs. A difference in the correlation coefficients computed in control and experimental sessions was observed, but it was difficult to deduce the effect of RFs on human health.

Auditory evoked potential patterns to voiced and voiceless speech sounds in adult developmental dyslexics with persistent deficits.

Auditory evoked potentials (AEPs) were recorded from eight developmental dyslexic adults with persistent reading, spelling and phonological deficits, and 10 non-dyslexic controls to voiced (/ba/) and voiceless (/pa/) consonant-vowel syllables. Consistent with previous data, non-dyslexics coded these stimuli differentially according to the temporal cues that form the basis of the voiced/voiceless contrast: AEPs had time-locked components with latencies that were determined by the temporal structure of the stimuli. Dyslexics were characterized by one of two electrophysiological patterns: AEP pattern I dyslexics demonstrated a differential coding of stimuli on the basis of some temporal cues, but with an atypically large number of components and a considerable delay in AEP termination time; AEP pattern II dyslexics demonstrated no clear differential coding of stimuli on the basis of temporal cues. These data reveal the presence of anomalies in cortical auditory processing which could underlie persistent perceptual and linguistic impairments in some developmental dyslexics. Furthermore, scalp AEP distribution maps showing the difference observed between /ba/ and /pa/ activity over time suggest that the regions implicated in the processing of crucial time-related acoustic cues were not systematically lateralized to the left hemisphere like they were for non-dyslexics. These findings may be conducive to a better understanding and treatment of perceptual dysfunctions in developmental language disorders.

Analysis of auditory evoked potential parameters in the presence of radiofrequency fields using a support vector machines method.

The paper presents a study of global system for mobile (GSM) phone radiofrequency effects on human cerebral activity. The work was based on the study of auditory evoked potentials (AEPs) recorded from healthy humans and epileptic patients. The protocol allowed the comparison of AEPs recorded with or without exposure to electrical fields. Ten variables measured from AEPs were employed in the design of a supervised support vector machines classifier. The classification performance measured the classifier's ability to discriminate features performed with or without radiofrequency exposure. Most significant features were chosen by a backward sequential selection that ranked the variables according to their pertinence for the discrimination. Finally, the most discriminating features were analysed statistically by a Wilcoxon signed rank test. For both populations, the N100 amplitudes were reduced under the influence of GSM radiofrequency (mean attenuation of -0.36 microV for healthy subjects and -0.60 microV for epileptic patients). Healthy subjects showed a N100 latency decrease (-5.23 ms in mean), which could be consistent with mild, localised heating. The auditory cortical activity in humans was modified by GSM phone radiofrequencies, but an effect on brain functionality has not been proven.

[Moderate aortic stenosis and aorto-coronary bypass]. / Sténose aortique modérée et pontages aorto-coronaires.

The presence of aortic stenosis in a patient facing surgical coronary revascularisation is a common situation. A tight aortic stenosis justifies combining aortic valvular replacement with the anticipated bypass. The discovery of a "moderate" aortic stenosis before coronary surgery poses a much more difficult problem. Moderate stenosis equates to aortic area values >0.6 cm2/m2 body area and <1.2 cm2/m2. An estimation of the progression of the stenosis following coronary surgery is fundamental to making the best possible decision but remains very difficult for a given individual. The factors to be taken into account are the aetiology of the stenosis, its severity, the valvular anatomy (calcification), associated coronary artery disease, the age of the patient and the progression of stenosis from one echography to the next. For each patient the risk/benefit ratio of the strategy must therefore be evaluated as much as possible (double procedure at once, or bypass followed by surveillance of the aortic stenosis). In order to do this it is necessary to consider, apart from the stenosis progression factors, the patient's life expectancy and point of view, as well as of course the operative risk (LV function, comorbidity...). Day to day experience shows that the degree of the stenosis is often under-estimated in patients facing coronary surgery, owing to a simple measurement of the gradient. Complete and accurate investigation of the aortic stenosis with Doppler often allows a definitive decision on the most suitable therapeutic approach.

[Impact of advances in transthoracic imaging on the indications for transesophageal echocardiography]. / Impact des progrès en imagerie transthoracique sur les indications de l'échocardiographie par voie transoesophagienne.

Technical advances have considerably improved the quality of imaging by transthoracic echocardiography in recent years. This has allowed access to information formerly reserved for transoesophageal investigation. As a result, certain changes in the indications of transoesophageal echocardiography have come about in clinical practice. The best example is probably in the evaluation of mitral regurgitation. The possibilities of accurate description of mitral valve anatomy and of reliable quantification of the lesion have reduced the indications of transoesophageal echocardiography in this pathology. In other indications, such as suspected endocarditis, the investigation of systemic embolism or dissection of the aorta, transoesophageal echocardiography is irreplaceable but the additional information obtained compared with transthoracic echocardiography is less.

[Role of echocardiography prior to to conservative treatment of mitral valvulopathy]. / Place de l'échocardiographie avant un geste conservateur pour valvulopathie mitrale.

Echography is a key investigation in the diagnosis and follow up of patients with mitral valvulopathy. Recent advances in transthoracic imaging allow precise evaluation of the entire mitral apparatus in the majority of patients, which avoids recourse to the esophageal route especially for mitral insufficiency. On the other hand, TEE remains systematic in cases of stenosis when percutaneous commissurotomy is envisaged to look for intra-cavitary thrombosis. Echographic analysis has the objectives of defining the anatomical mechanism of the leak or stenosis, addressing aetiological arguments, quantifying the valvular dysfunction, and finally appreciating its repercussions (size of the left atrium, left ventricular function, pulmonary pressures). These elements, as well as evaluation of the symptoms, influence the therapeutic indications. The feasibility of conservative action, for which the significance compared to valvular replacement is known, depends directly upon the anatomical lesion and influences the therapeutic indications, especially in asymptomatic subjects for whom recent recommendations have been published. The experience of the ultrasonographer in the evaluation of mitral valvulopathies and his knowledge of conservative techniques allows improvement of the therapeutic discussion with the patient, the surgeon and the catheteriser. Performing TEE in the operative suite prior to conservative mitral surgery is practiced in many centres, as well as checking at the end of the procedure, especially for complex plasties. Three dimensional echography can currently be performed routinely by the transesophageal route, and probably in the near future by the transthoracic route, thanks to the recent arrival of real time 3D. Exercise echography also promises an important development thanks to the commercialization of new effort tables, and will allow refinement of the therapeutic indications in patients with few symptoms or for whom there is a discordance between the objective data and the functional status, but the therapeutic implications of this investigation remain to be defined.

[Usefulness of intraoperative echocardiography for the management of mitral regurgitation]. / Intérêt de l'échocardiographie peropératoire dans la prise en charge des insuffisances mitrales.

Intraoperative transesophageal echocardiography is crucial in the management of patients with mitral regurgitation. In fact, a vast majority mitral insufficiencies may actually be repaired. This kind of surgery require an excellent definition of anatomic lesions and mechanisms of mitral regurgitation in order to optimize the result of the repair. In this field, intraoperative echocardiographic findings are complementary with anatomical findings for the surgeon. Before surgery, intraoperative echography help to describe all valvular lesions and mechanisms of the regurgitation. Three-dimensional echocardiography may be obtained using intraoperative echography and may be useful in mitral valve prolapse to better define the location and size of prolapse and to communicate informations to the surgeon. After repair, echographyallow the control of the result and also of right and left ventricular function. In case of major abnormality such as residual significant mitral regurgitation or important intra-ventricular obstruction, a second procedure may be required. The collaboration between the echographist and the surgeon is crucial to obtain the best results in mitral valve repair. Indications for intraoperative echocardiography are dependent on the experience of the surgeon and the complexity of mitral lesions to repair.

Imaging in evaluation of response to neoadjuvant breast cancer treatment benefits of MRI.

PURPOSE: To compare the value of conventional imaging modalities and MRI for determination of response to neoadjuvant chemotherapy for breast cancer. MATERIAL AND METHODS: Sixty tumors (53 ductal carcinomas, seven invasive lobular carcinomas) in 51 patients were evaluated by physical examination, mammography, ultrasound, and MRI at baseline before therapy, after three courses of chemotherapy, and after six courses prior to surgery. Data from physical examination and imaging studies were compared to histopathological findings. RESULTS: (i) MRI was the most reliable technique for evaluation of residual tumor size; this parameter was correctly estimated in 63% of cases by MRI versus, respectively 52, 38, and 43% by physical examination, mammography, and ultrasound, (ii) MRI correctly identified the response to chemotherapy in all cases of complete response (five cases), and in 45/55 cases of partial response (43 cases) or no response (12 cases), and (iii) among the 32 patients who underwent a mastectomy, MRI correctly revealed the multifocal nature of the disease for 12/15 multifocal lesions found at histological examination; both mammography and sonography were accurate in only six of the 15 cases. CONCLUSION: MRI appears to be a valuable technique for assessment of response to chemotherapy and identification of multifocal disease prior to surgery.